Patient Interface Plenum Design for Deadspace and CO2 Washout
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Solution Overview
Problem
Existing respiratory therapy devices and systems, such as CPAP and NIV, face challenges with discomfort, poor fit, noise, complexity, and reduced patient compliance due to inadequate seal-forming portions, bulky stabilizing harnesses, and inefficient CO2 washout systems, which affect the efficacy and comfort of treatment for respiratory disorders.
Innovation Solution
A patient interface with a plenum chamber and integrated volume-reducing members to minimize deadspace, separate therapy volume from deadspace, and incorporate a flow-directing mechanism to enhance seal integrity and reduce rebreathing of CO2, while maintaining positive air pressure therapy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the plenum chamber volume is reduced to minimize deadspace and CO2 rebreathing, then patient comfort and therapy effectiveness are improved, but the seal-forming portion may become less stable and difficult to seal against the patient's face
Solution Approach 1:
The patient interface is divided into distinct functional zones: a seal-forming portion that interfaces with the patient's face and a plenum chamber portion that delivers therapy pressure. This segmentation allows the seal-forming portion to be optimized for sealing stability while the plenum chamber can be minimized to reduce deadspace and CO2 rebreathing.
Solution Approach 2:
The seal-forming portion is extracted as a separate, dedicated component from the plenum chamber. This allows the seal-forming portion to be independently optimized for creating and maintaining a seal against the patient's face, while the plenum chamber volume can be minimized for therapy effectiveness without compromising seal stability.
2Reliability
If a bulky stabilizing harness is used to maintain seal integrity, then seal stability is improved, but patient comfort and ease of use are reduced
Solution Approach 1:
The patient interface is segmented into a lightweight seal-forming portion and a separate stabilizing harness. The seal-forming portion is designed to be as lightweight and comfortable as possible while the harness provides minimal necessary stabilization, reducing overall bulk and improving patient comfort.
Solution Approach 2:
The seal-forming portion is designed with localized sealing features concentrated at the interface with the patient's face, while the rest of the structure is minimized. This allows seal stability to be achieved through targeted local features rather than requiring a bulky overall structure, improving comfort and ease of use.
3Object-affected harmful factors
If the plenum chamber volume is minimized to reduce deadspace, then CO2 rebreathing is reduced and therapy effectiveness is improved, but the device complexity increases due to integrated volume-reducing members
Solution Approach 1:
The volume-reducing members are integrated into the plenum chamber structure itself, combining the deadspace reduction function with the existing therapy delivery structure. This merging approach minimizes additional complexity while achieving the goal of reducing deadspace volume to prevent CO2 rebreathing.
Solution Approach 2:
The plenum chamber structure serves multiple functions: delivering therapy pressure, providing structural support, and incorporating volume-reducing features to minimize deadspace. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity while achieving deadspace reduction.
Data Source
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Figure 1C
AI summary
The present invention relates to a patient interface for sealed delivery of a flow of air at a continuously positive pressure with respect to ambient air pressure to an entrance to the patient's airways including at least an entrance of a patient's nares, wherein the patient interface is configured to maintain a therapy pressure in a range of about 4 cmH2O to about 30 cmH2O above ambient air pressure in use, throughout the patient's respiratory cycle, while the patient is sleeping, to ameliorate sleep disordered breathing; said patient interface comprising: a cushion assembly configured to form a seal around the patient's nose and/or mouth, the cushion assembly forming a plenum chamber pressurised at a pressure above ambient pressure in use; a gas washout vent configured to allow a flow of patient exhaled CO2 to an exterior of the patient interface to minimise rebreathing of the exhaled CO2 by the patient; a heat and moisture exchanger provided within the plenum chamber configured to be between the patient's airways and the gas washout vent; at least one pressurization port provided to an anterior side of the heat and moisture exchanger; and at least one seal member arranged to separate the plenum chamber into a main chamber and at least one peripheral chamber, the main chamber comprising a main volume of the plenum chamber for delivery of the therapy pressure, and the at least one peripheral chamber comprising a deadspace volume of the plenum chamber, wherein the main volume is configured to be in direct fluid communication with at least the entrance to the patient's nares and the gas washout vent, and wherein the heat and moisture exchanger is positioned within the main chamber; wherein the at least one pressurization port is arranged to allow the pressurization of the at least one peripheral chamber independently of the main chamber.